In an ultrasonographic diagnosis using an ultrasonographic device, information on a boundary (contour) of an organ or the like to which attention is paid is effective information. For example, with respect to an organ such as a heart or the like, it is effective to diagnosis that a boundary (contour) of the left ventricle is extracted and the area surrounded by the boundary (contour) concerned is determined or the volume of the left ventricle is estimated on the basis of the boundary (contour).
For example, a prior art described in Patent Document 1 is known as a technique of extracting and displaying a boundary (contour) of a tissue.
Patent Document 1: JP-A-8-206117
According to the prior art disclosed in the Patent Document 1, the local maximum point of a scalar quantity representing the gradient of an image signal at each point in a tomogram is determined and the boundary (contour) of the tissue is drawn from the local maximum points.